Extended backside-illuminated InGaAs on GaAs IR detectors

Diode structures of short wavelength infrared (SWIR) InGaAs material were grown epitaxially on 3" GaAs substrates by molecular beam epitaxy. Despite the large lattice mismatch of 6% between In_0.8Ga_0.2As and GaAs the diode performance allows applications in spectroscopy and imaging. Photovoltaic diode characterization measures like R₀A product and quantum efficiency were extracted from I-V curves. The layers are processed with standard photolithography and micro-structuring tools and finally flip-chip bonded on a silicon read out integrated circuit (ROIC). Linear arrays of 256 and 512 pixel with 25 μm pitch were fabricated as well as focal plane arrays (FPA) of 256 × 320 pixel with 30 μm pitch. Functionality is proven by using the assemblies in systems for spectroscopy and beam profiling up to 2.5 μm wavelength.